Micro-gasifier array networking

ABSTRACT

A method is described for integrating a plurality of micro-gasifiers comprising gasifiers, filters, and engine sets or turbine gensets or combined cycle gensets by linking them via a common bus wherein air flow and engine fuel flow is regulated by valves controlling gas flow between the bus and engine genset or turbine genset or combined cycle genset.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/269,817 filed on Sep. 19, 2016, which is a continuation-in-part ofU.S. patent application Ser. No. 14/448,007 filed on Jul. 31, 2014, nowU.S. Pat. No. 9,469,821, which claims priority to U.S. ProvisionalPatent Application No. 61/867,716 filed on Aug. 20, 2013, the contentsof which are incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The invention broadly relates to micro-gasifier array networking.

BACKGROUND OF THE INVENTION

Micro-gasifiers were used extensively in Europe during World War II topower internal combustion engine vehicles while conventional gasolinewas very difficult to obtain. The basic operating principles of suchdevices will now be described. Initially, dry biomass is combusted in anenclosed container under a mild vacuum as generated by the intakemanifold of a reciprocating piston engine. Air inlets and gasifieroutput stream connections are arranged so that the biomass is onlypartially combusted, resulting in an exhaust stream which containscarbon monoxide and may additionally contain hydrogen and hydrocarbongasses. This gas can be further combusted in an internal combustionengine to produce shaft power.

FIG. 1 (prior art) illustrates a typical layout of such devicesincluding gasifier, filter, startup and turn off flare, air mixingvalves and an internal combustion engine. The normal startup procedureis to light the gasifier and bring it up to a temperature which producesa sufficient amount of combustible gasses to at least idle the attachedinternal combustion engine. This is typically done by initially routingthe output of the gasifier to a flare device, which protects operatingpersonnel from the highly toxic carbon monoxide gas generated by thegasifier. Various schemes for initiating airflow through the gasifierare used such as incorporating an aspirating pump in the flare device oran inline blower in the flare device, thus creating a partial vacuum inthe gasifier. Alternatively, an input blower can be utilized on thegasifier to force air through the system. However, this is generallyregarded as less desirable because positive pressure in the gasifierdevice can result in highly toxic carbon monoxide gas leakage fromvarious system components such as monitoring ports, biomass feed and ashports, and various system interconnections.

Once airflow is set up through the gasifier, its combustion zone can belit by any of the various techniques used to start a wood fire, withinitiation by a propane torch device being one of the most commontechniques in current use. Dependent upon the size of the gasifier, andthe oxidation state and moisture content of the biomass fuel located inthe gasifier, startup will typically take three to 30 minutes. In orderto maintain area safety, the flare should be equipped with an igniterwhich burns escaping carbon monoxide gas. Once a sufficient quantity ofcombustible gases are present in the gasifier output stream, the flarevalve is closed, the genset gasifier valve is opened and the attachedengine is cranked with dynamic adjustment to the air inlet valve inorder to provide a combustible mix suitable for firing the enginecylinder(s). In normal operation the engine's displacement revolutionrate (RPM) and load demands provide a degree of regulation the inputairstream to the gasifier and thus the rate at which biomass is consumedin its internal partial combustion process. This partial combustionprocess typically consumes all of the oxygen in that input stream so theair inlet valve on the engine is adjusted to provide enough oxygen for asuitable air fuel ratio for the desired output power.

On turn off the engine's ignition system and/or its air supply valvesare turned off, which stops the engine and stops flowing air through thegasifier. The gasifier core temperature may be well above 1,000 degreescentigrade and the system may be equipped with multiple layers ofinsulation so that it will typically take several hours for the gasifierto cool down to room temperature. Restart delay is typically directlyproportional to the amount of time the gasifier has been off, with shutdown durations of a few minutes resulting in nearly instantaneousrestart due to the residual combustible gases retained by the system andthe high combustion zone core temperature.

Internal combustion engines typically produce peak operating efficiencyat a specific design point. Such a design point is dominated byfrictional and accessory losses on the low side and non-optimalcombustion dynamics on the high end particularly if the engine designershave pushed the peak output rating of the engine past the optimalcombustion operating region. Likewise, the gasifier is limited by heatlosses on the low end which will limit the internal core temperatureand, thus, the gasification rate and quality. At the high end, gasifiersystem constraints like biomass mass flow, air mass flow, air jettinggeometry and hot zone geometry limit the gasifier's performance.Consequently, the combination of the gasifier and internal combustionengine will typically result in a fairly narrow power range for peakoperating efficiency.

SUMMARY OF THE INVENTION

Embodiments of the invention are directed toward micro-gasifier arraynetworking.

One embodiment of the invention is directed toward an apparatuscomprising: a multi-gasifier array comprising a common gasifier bus ormulti-tap pipeline connecting two or more micro-gasifier systems; and aplurality of valves for regulating the flow of gas within themicro-gasifier array. This gas can include air, syngas, externalhydrogen, or external natural gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a typical micro-gasifier layout.

FIG. 2 is a diagram illustrating a multi-gasifier array comprising acommon gasifier bus or multi-tap pipeline connecting two or moremicro-gasifier systems.

FIG. 3 is a diagram illustrating a multi-gasifier array comprising acommon gasifier bus or multi-tap pipeline connecting two or moremicro-gasifier systems.

FIG. 4 is a diagram illustrating another multi-gasifier array comprisinga common gasifier bus or multi-tap pipeline connecting two or moremicro-gasifier systems.

FIG. 5 is a diagram illustrating present invention with multiple fuelinputs and a fuel gas manifold feeding to multiple possible gensets.

DETAILED DESCRIPTION

In the following paragraphs, embodiments of the present invention willbe described in detail by way of example with reference to the attacheddrawings. Throughout this description, the preferred embodiment andexamples shown should be considered as exemplars, rather than aslimitations on the present invention. As used herein, the “presentinvention” refers to any one of the embodiments of the inventiondescribed herein, and any equivalents. Furthermore, reference to variousfeature(s) of the “present invention” throughout this document does notmean that all claimed embodiments or methods must include the referencedfeature(s).

Embodiments of the invention pertain to the use of two or moremicro-gasifier systems in an application where: (i) the demand for shaftpower varies widely and rapidly over time, and (ii) biomass conversionefficiency is important such as in an electrical micro-grid.

FIG. 2 illustrates a multi-gasifier array 100 comprising a commongasifier bus 110 or multi-tap pipeline connecting two or moremicro-gasifier systems 120, such as the gasifier described with respectto FIG. 1. In the illustrated embodiment, each gasifier system 120comprises a gasifier 130, a filter 140 and an engine genset 150. Theinteraction between the gasifier bus 110 and each micro-gasifier system120 is defined by the dynamic control of four airflow valves 155, 160,165, 170 as depicted in FIG. 2. Several modes of operation are possiblewith this geometry, thus providing enhanced system throughput efficiencyas compared to a simple array of isolated units, i.e., without thegasifier bus interconnects.

FIG. 2 depicts the use of a number of valves including Valve 1 (155),Valve 2 (160), Valve 3 (165), and Valve 4 (170). Although four valvesare employed in this embodiment, any number of valves may be employedwithout departing from the scope of the invention. In order to explainthe modes of operation of the multi-gasifier array, the function of eachof the valves will now be described.

Valve 1 comprises the gasifier output valve 155. This valve 155regulates the rate in which air is drawn through the gasifier 130.

Valve 2 comprises the gasifier bus valve 160. This bi-directional valve160 regulates the flow of gas from the gasifier 130 to the gasifier bus110, or the flow of gas from the bus 110 to the engine, or closes toisolate the system from the bus 110.

Valve 3 comprises the engine fuel input valve 165. This valve 165regulates the amount of input gas to the engine and is partiallyresponsible for regulating the amount of vacuum or the pressure deltabetween the gasifier bus 110 and atmospheric conditions.

Valve 4 comprises the engine air input valve 170. This valve 170, inconjunction with Valve 3 (165): (i) regulates the air fuel mixture tothe engine, and (ii) regulates the amount of vacuum generation orpumping action by the engine.

Still referring to FIG. 2, a large number of operating modes arepossible with the illustrated gas flow network configuration. Several ofthe key operating modes will now be described.

Mode A comprises conventional isolated system operation. In this mode,Valve 1 (155) is opened, Valve 2 (160) is closed, and Valves 3 and 4(165, 170) are modulated by the engine controller, which can be eitherautomatic or manually controlled in order to produce the desired poweroutput. Mode A requires the gasifier 130 to be at operating temperature.

Mode B comprises flareless gasifier startup. Under this mode, one ormore arrayed systems 120 are operating at power and it is desired tobring one or more additional gasifiers on line. In Mode B, Valves 1, 2and 4 (155, 160, 170) of one or more operational systems are adjusted todraw gas from the gasifier bus 110 in addition to the gas stream comingfrom the local gasifier 130. This creates a partial vacuum on thegasifier bus 110, which initially is filled with air, thus offsettingpart of the flow normally supplied by Valve 4 (170). The air supply tothe gasifier bus 110 is provided by a system in startup mode whereValves 1 and 2 (155, 160) are open and Valves 3 and 4 (165, 170) areclosed, thereby drawing air through a non-burning gasifier to supplysome of the air required to power one or more operating system engines.This gasifier 120 is then lit by any conventional means and as itsgeneration of combustible gasses increases, Valve 4 (170) in thecorresponding gas receiving engine(s) is adjusted to maintain proper airfuel ratio. Once this gasifier 120 is up to operating temperature, alloperating systems can switch to Mode A (including this freshly startedgasifier) by cranking and starting its corresponding engine.

Mode C comprises gasifier shutdown. It is desirable to utilize theresidual gasses in the gasifier 120 on shutdown in order to minimize theleakage of carbon monoxide gas into the surrounding environment and tomake effective use of the stored thermal energy in the gasifier 120.Under this mode of operation, when the gasifier system 100 is shut down,first its engine is turned off by closing Valves 3 and 4 (165, 170) andopening Valve 2 (160), thereby allowing the operating gasifier 120 tocontribute to the overall system. Next, Valve 1 or 2 (155 or 160) isgradually throttled back to shut down and cool the gasifier 120 in anorderly fashion.

One or more bus systems must adjust Valves 2, 3 and 4 (160, 165, 170) toutilize the gas flow generated by this gasifier 120 as it ramps fromcombustible gas mode down to a low flow of gas which contains someresidual oxygen.

Mode D comprises hot idle. In order to maintain fast response capabilityto transient load requirements, it can be desirable to keep one or moregasifiers 120 at hot idle so that they can ramp quickly to produce largequantities of combustible gasses when needed. This can be accomplishedby turning off their corresponding engines and holding them at low flowrates, as described in Mode C. As an alternative control scheme, theymay be pulsed between high and low flow levels using the same technique.

Mode E comprises peak power generation. If the system enginesincorporate modern electronic ignition controls, they can be configuredto rapidly start and run in a fashion similar to the start/stopoperation of many late model cars that turn their engines off atstoplights and start very quickly when the throttle is applied. Thus,the engines can ramp much faster than the gasifiers 120. However,operating gasifiers have substantial filter volumes filled withcombustible gasses such that one or more engines running at full powercan contribute a small amount of gas from their filter tanks to otherengines without substantially reducing their power output. In this modeof operation, Valve 2 (160) is opened on one or more systems operatingat power and Valves 2, 3 and 4 (160, 165, 170) are opened with Valve 1(155) closed on additional systems which are currently in the off stateto provide rapid transient power response.

In some embodiments, multi-mode operation is employed. As would beappreciated by those of ordinary skill in the art of networkingtopology, multiple modes of operation are possible, particularly in alarge array of systems, without departing from the scope of the presentinvention. In such systems, attention must be paid to the complexity ofthe interconnecting bus lines.

FIG. 3 is a diagram illustrating a multi-gasifier array 200 comprisingmultiple gasifier busses 110 with multiple Valve 2 interconnects 210. Inorder to support multiple gasifier systems running in different modes,it may be desirable to have multiple gasifier busses 110 with multipleValve 2 interconnects 210. However, the system complexity and costassociated with additional valves and the dead volume and residual gasvolumes associated with occasional use of various modes becomes alimiting factor. Although it is always possible to highly optimize asystem topology when use pattern is highly regular, certain tradeoffsmust be made in the real world between versatility versus networkcomplexity.

FIG. 3 depicts an example large network topology in which a physicalarray of 112 gasifier systems 120 is laid out as fourteen rows of eightgasifiers. The row configuration is selected to allow service access toindividual gasifier systems 120 and efficient interconnects of thevarious feeds and physical wiring. Each of the gasifier systems 120 in arow is connected to gasifier systems in a common bus 110 that is theneight gasifiers long. The individual row gasifier lines are thenconnected to crossbar trunk lines 220, which span the entire array 200to individual Valve 5 s (230). One to three of these crossbar trunklines 220 may be suitable.

FIG. 4 is a diagram illustrating an additional multi-gasifier array 300comprising multiple gasifier busses 110. This topology features multiplerow/column (i.e., crossbar) interconnect patterns, and can also includebus isolation valves 310 in line on each of the gasifier column and rowbusses as Valve 6 (310). The illustrated topology also includes a secondcrossbar trunk line 220. Of course, a wide range of other topologies arepossible without departing from the scope of the invention.

In some embodiments, multiple gasifier bus lines 110 with multiple Valve2 (160) connections as Valve 2, Valve 2′, Valve 2″, etc. may be utilizedin gasifier/engine configurations which produce outputs in addition toelectricity such as process hydrogen, and/or biochar.

A diagram illustrating this multiplicity of outputs as well asmultiplicity of engine/generator configurations is shown in FIG. 5. Asystem of directly heated gasifiers 430 or indirectly heated gasifiers435 gasify cellulosic biomass to produce biologically derived syngas andcarbon. The resulting bio-syngas is fed to fuel gas manifold 480 andsyngas flow out of gasifiers 430 or 435 is controlled by Gasifier Valve1, 1′, 1″, etc (455) which regulate the flow out of each gasifier tofuel gas manifold 480. The generated syngas can also alternatively bedirected to a hydrogen generator 410 which comprises a system forgenerating hydrogen from multiple sources and for separating hydrogenfrom a gas mixture. The carbon from either the indirectly heatedgasifier or directly heated gasifier can be directed to the hydrogengenerator where additional gasification occurs for the purpose ofproducing syngas in the presence of steam or hydrogen in the presence ofnatural gas. Hydrogen is generated from the following reactions in thepresence of carbon or methane from natural gas:

C+H₂O→H₂+CO  [1]

CH₄+H₂O→3H₂+CO  [2]

C+CH₄→2H₂+2C  [3]

Reaction 3 decarbonizes natural gas by reacting natural gas on thesurface of a biocarbon and produces, in addition to hydrogen, a finecarbon which has utility as commercial industrial carbon (e.g. carbon intires, activated carbon, etc.). A carbon resulting from the directgasification can also alternatively be sequestered for long term storagein soils as biochar.

Fuel manifold 480 regulates the flow of input fuels natural gas,hydrogen from the hydrogen generator, or bio-syngas from the gasifiersto gensets 450, 452, 453 via Engine Fuel Input Valves 3, 3′, 3″, etc.(465). Genset 450 may be a piston engine generator such as a reciprocalinternal combustion engine connected to a generator. Genset 452 refersto a turbine or microturbine generating electricity. Genset 453 refersto a combined cycle system which uses waste heat from a gas turbine androutes it to a steam turbine, thereby generating extra electricity. Flowof fuel or air to the common bus 410 is achieved via Bidirectional BusValves 2, 2′, 2″, etc. (460). Air flow from ambient to gensets 450, 452,453 is regulated by Air Input Valves 4, 4′, 4″, etc. (470).

All previously discussed operating modes A-E may be implemented duringoperation of the interconnected systems in FIG. 5. Extra flexibility isprovided in the ability to input natural gas or hydrogen as fuel in thecombustion process. Management of gas flow within the bus is performedby drawing air or syngas or hydrogen or natural gas from the gasifierbus and creating a partial vacuum on the gasifier bus which is initiallyfilled with air, thus ensuring regulation of a pressure delta betweenthe gasifier bus and atmospheric conditions. The bi-directional gasifierbus valves may also be used to regulate the flow of air or syngas orhydrogen or natural gas from the gasifier or hydrogen generator to thegasifier busses or the flow of air or syngas or hydrogen or natural gasfrom the gasifier busses to the engine genset or turbine genset orcombined cycle genset. Multiple gasifier busses may be interconnected asshown in FIGS. 3 and 4 using the gasifier system of FIG. 5 as the basicunit.

The present method for operating an array of micro-gasifiers enablesoperation of the array in a manner that maximize economics, fuelutilization, or minimizes carbon emissions. For example, production ofcarbon neutral electricity is achievable by inputting natural gas andoffsetting the emissions from the natural gas combustion withcorresponding production of sequesterable biochar. Carbon neutral modecan be run in a manner that maximizes natural gas use or biomass use,leading to different economic results due to different feedstock costs.Similarly, an operating mode can be implemented which decarbonizesnatural gas and produces hydrogen in addition to carbon neutralelectricity and commercial carbons. In some embodiments, the hydrogenproduction is maximized at the expense of reduction in emissions byinputting the commercial carbon into the gasifier.

One skilled in the art will appreciate that the present invention can bepracticed by other than the various embodiments and preferredembodiments, which are presented in this description for purposes ofillustration and not of limitation, and the present invention is limitedonly by the claims that follow. It is noted that equivalents for theparticular embodiments discussed in this description may practice theinvention as well.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not of limitation. Likewise, the various diagrams maydepict an example architectural or other configuration for theinvention, which is done to aid in understanding the features andfunctionality that may be included in the invention. The invention isnot restricted to the illustrated example architectures orconfigurations, but the desired features may be implemented using avariety of alternative architectures and configurations. Indeed, it willbe apparent to one of skill in the art how alternative functional,logical or physical partitioning and configurations may be implementedto implement the desired features of the present invention. Also, amultitude of different constituent module names other than thosedepicted herein may be applied to the various partitions. Additionally,with regard to flow diagrams, operational descriptions and methodclaims, the order in which the steps are presented herein shall notmandate that various embodiments be implemented to perform the recitedfunctionality in the same order unless the context dictates otherwise.

Although the invention is described above in terms of various exemplaryembodiments and implementations, it should be understood that thevarious features, aspects and functionality described in one or more ofthe individual embodiments are not limited in their applicability to theparticular embodiment with which they are described, but instead may beapplied, alone or in various combinations, to one or more of the otherembodiments of the invention, whether or not such embodiments aredescribed and whether or not such features are presented as being a partof a described embodiment. Thus the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture.

A group of items linked with the conjunction “and” should not be read asrequiring that each and every one of those items be present in thegrouping, but rather should be read as “and/or” unless expressly statedotherwise. Similarly, a group of items linked with the conjunction “or”should not be read as requiring mutual exclusivity among that group, butrather should also be read as “and/or” unless expressly statedotherwise. Furthermore, although items, elements or components of theinvention may be described or claimed in the singular, the plural iscontemplated to be within the scope thereof unless limitation to thesingular is explicitly stated.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “module” does not imply that the components or functionalitydescribed or claimed as part of the module are all configured in acommon package. Indeed, any or all of the various components of amodule, whether control logic or other components, may be combined in asingle package or separately maintained and may further be distributedacross multiple locations.

Additionally, the various embodiments set forth herein are described interms of exemplary block diagrams, flow charts and other illustrations.As will become apparent to one of ordinary skill in the art afterreading this document, the illustrated embodiments and their variousalternatives may be implemented without confinement to the illustratedexamples. For example, block diagrams and their accompanying descriptionshould not be construed as mandating a particular architecture orconfiguration.

1. A multi-gasifier array, comprising: a physical array ofmicro-gasifier systems under vacuum including a plurality of gasifierrows and columns interconnected via gasifier column and row busses, aplurality of gasifier busses connected by a plurality of bi-directionalgasifier bus valves, with each gasifier bus connecting two or moremicro-gasifier systems, each micro-gasifier system comprising agasifier, a filter and a genset; and a plurality of airflow valves,including the bi-directional gasifier bus valves to regulate the flow ofgas or hydrogen or natural gas via differential vacuum from the gasifierto the gasifier busses or the flow of gas or hydrogen or natural gas viadifferential vacuum from the gasifier busses to the engine genset orturbine genset or combined cycle genset.
 2. The multi-gasifier array ofclaim 1, wherein the genset comprises an engine genset, a turbine gensetor a combined cycle genset.
 3. The multi-gasifier array of claim 1,wherein each of the micro-gasifier systems in a row is connected toother micro-gasifier systems in a common bus.
 4. The multi-gasifierarray of claim 3, wherein each common bus is connected to one or morecrossbar trunk lines, which span the entire array.
 5. The multi-gasifierarray of claim 3, further comprising a bus isolation valve in line oneach of the gasifier column and row busses.